In the detector device in the prior art for CT security inspection system, a detector array in the detector module is arranged on the positioning support, an adjustable collimator is generally installed in front of the detector module, thereby, the entire detector device is structured. The structured detector device described above has the following shortages and problems: first, the volume of the detector device employing the above structure is too big, therefore, the space occupied by the entire CT security inspection system is increased; second, since it is required to adjust related position relationship among the radiation source, the collimator, the detector module and the positioning support, the adjusting operation, especially the adjustment for the collimator, is complicated, so that the installation and the regulating for the position of the detector device are inaccurate. Furthermore, since the sealing of the detector device is not very good, the detector crystal has a poor working stability.